Blast cleaning



Sept. 22, 1953 F. NEWELL BLAST CLEANING Filed Nov. 5, 195o INVENTOR.F/P/M//f NEM/[M Patented Sept. 22, 1953 FrankNewell,l Chicago', Ill.,assigner to Pagborn; Corporation,.Hagcrstown, Md., a corporation o1Maryland ppicati-GiiNbv'emh'er 3, 1950, Serial N0. 193,903

1 rIhis invention relates te the cleaning otrmaterials and moreparticularly to a pressure bla-sting machine and method for projectingastream of soft abrasive particles or grit against ai surface! to removesuperuous materials such as grease's, carbon and dirt therefrom-Soft'grit'iolasting of fragile electrical andY motor parts, etc., vas ameans` of removing heavy, hard. coating of grease,` carbon, dir-t, etc.,is of great interest to industry. The widespread trend tcward greaterindustrial plant safety hasv given impetus to`l the use of.so'ft Agrits'due to the toxic hazards ofv previouslyl used solventv typevchemicals'.. Typical soft grits arev celluloisc'- materials such asground corn. cubs, wood particles'y (saw dust), riceA hulls,.- ground'walnut or pecan shells or' ground. pits of fruits Alike peach, apricot,etc., and are usually particles of about to e0 mesh or smaller.V

The use of prior art blasting equipment to blast theseusoft grits hasnot. been satisfactory, particularly with` the smaller sized particleswhich are more. desirable by reason ofthe better and more economicalcleaning they effect. These particles do not feed themselvesproperly tothe blasting mechanism` Whether pressure,` suction, gravity orcombinations of these forces areused to carryl them to the. mechanism.Instead of moving smoothly the particles have -a tendencyI to bridge orpack (jam): in the passageway theyv move through. As azresult the: flowoi particles is cut off and, where the feeding; force isv large enough,the jammed particlesV suddenly break` loose in excessive amounts.Thisfeast-or-famine operation continues inl` short cycles. and`necessitates careful attention to assure thorough cleaning.

It is among the objects of this invention tof provideA an improved?.blasting machine and method for proiectinga stream of soft abrasiveswithout the: above diniculties- Another.' object' of the invention isto. provide-V Va machine that willi allow a small flow of soft grit athigh` pressure, or a heavy solid now ofv soft grit at low pressurefor'cleaning; heavy grease or light oil lm'seiiiciently from: variousmachine with reference i tov f the lappended drawings whereinz.'

lig. 1A isi a" frontvie'w of. a pressure blasting.V machine of thepresenti invention, yportions of ther.

machinev being; broken away to-show details,vv`

Fig. 2 is a plan View ci*` the machine shown in Fig. 1,:

Figs. 3 and 4 are vertical cross-section views of a mixing chamberportion of the machine of Figs. 1 andl 2`, thev chamber being shown Iinvdifferent. operating positions, and

Fig. 5 is a vertical cross-section view at right anglesrto those ofFigs. S'and. 4 of the mixing and projecting portions' or the apparatusof' Figs. 1 and2.

The machine o'i the iig'nrescomprises a tani: t@ for receiving andstoring a quantity of abrasive particles.v The bottom portion ofthe tankle is in the `forni of a hopper. I2`having an opening ifi (see Fig. 5)forV discharging the abrasive. Agitating means te', consisting;preferably of a condui't f6 having a pluralityof' downwardly directedholes iB; extends withinK and across the tank iii for` dischargingaplurality of; uid streams 2e into the abrasive holding` hopper i2 inorder to' assure that the abrasive particles are uniformly dischargedandy doi not` jam theu hopper i2 or the opening t4". This opening is'connected through an abrasivey control: valve mechanism i2? to" a mixingchamber' 21 where the particles dischargedfromI thel hopper are mixedwith the propeliant fluidi in thiscas'e air. Mixing chamber22- has anopening 24i for'receivin'g'- a stream of air under pressure'fforimparting" a projecting forceL upon' said abrasive particles dischargedfrom* hopper t2", `and a dis'e'ha.1geV opening 25?: for directing theyimpelled stream` ci' abrasive particles andi a-ir (seefiig. 515

The; machine. sncvm in Figs. rana' a induces. a erst conduit `ai fordelivering. uuid' to agitar-ieg.

' ber 22, and iromthenuidfsupply (not shown) respectively. A nozzle 134is connected-.by an ado'litionalA conduit to2., `shown asa flexiblehose, .to the. outflow opening 26 ofv chamber 22. The iiexiblei conduitsare attached in place by any suitablexarrangement such as the woodscrews Hill, or theelamps- HH.v Toprevent the. carrying baokofthe'blasting particles to thefval-ves @dal a set of check valves 98, 99are desirably inserted in conduits 30, 32:.

Thel` pressure; blasting 4.machine ofV Figs. i anc-1 2 is of theportable type supported on wheels 50, 52 mounted on axle 56 suitablysecured to the tank Ill. Framework 54 also secured to the tank forms astand to support the machine when it is rolled tothe desired position.This or an additional framework 55 can also be used to carry a coiled uplength of hose |32 or a source of compressed fluid.

A funnel 66 is provided in the top of tank I6 for guiding the abrasivesupply into a loading opening I3 in a concave top portion II forming theupper wall of the sealed-in tank storage space. A valve I1 seats inopening |3 for the purpose of opening and closing tank I to the flow ofabrasive from funnel 60. Handle means is connected as by flexible cable62 or chain to operate valve I1.

An abrasive control valve lever 13 is also provided at the top of tankI0 and connected through vertically extending rod 14 to arm 16 pivotedat 18 to the upper portion |23 of the abrasive control valve mechanism.|22. This portion is hollow and has an upper flange 92 clamped to aplate 94 at the bottom of the hopper, as by bolts |40, and a gasket |24seals this joint. Member |23 tapers down at its lower end to a smalltube 96 seated against a deformable rubber valve ring |05 held in asocket |06 in the upper portion of the mixing chamber 22. An upwardmovement of arm 16 moves a U-shaped clamp 11 about hinge 18 andcompresses the valve ring forcing it from the open position shown inFig. 4 to the closed position shown in Fig. 3. For regulating therequired movement of U clamp 11 a. compression adjustment screw 83 isalso provided. Modifications of this valve control mechanism can be madeas indicated in U. S. patents numbered 2,025,247 granted December 24,1935, and 2,146,917 granted February 14, 1939.

A clean out plate |36 fastened over an external opening |39 in hollowmember |23 is made readily removable and carries a valve slider |31(partly broken away in Fig. 1) which can be received in grooves |38 ofenlarged portion |23 to shut off the supply of abrasive. The mixingchamber 22 can be removed from the tube portion 96, and when this isdone it is advisable to first remove the plate |36, and then reverse andreplace it so that slider |31 is in cut-off position. To improve thecut-off operation, the grooves |38 can be located against the upper wallof member |36 so that abrasive cannot flow out over the top of slider|31 and through opening |39 when the plate |36 is not fully seated. Sucha construction is shown in the above-mentioned U. S. Patent No.2,146,917. Plate |36 can also be removed to permit convenient inspectionand cleaning of this member. An exhaust valve 2| for selectably openingtank I0 to the atmosphere facilitates its cleaning and opening whenrequired. A capped handhcle 88 (Fig. 2) at about mid-tank height,enables the insertion of a hand or suitable cleaning or exploring toolinto substantially all portions of the tank interior.

Mixing chamber 22 has a converging passageway |26 through which itcarries the stream of fluid under pressure and in which is mixed theabrasive particles. This convergence which may be about 5 to 10 degreesassures that there is no blocking offset in the abrasive-carrying borewhere the mixing chamber 22 meets the conduit A feature of the abovemachine is the maintenance of above-atmospheric pressure in the tankIII) during the blasting. This is provided by the fluid under pressurethat is admitted through conduit 30. To assist in controlling thepressures, meters 95, 96 are conveniently connected to the conduits 30,32.

With a blast hose |32 having a one-inch diameter, a nozzle |34 having a1% inch diameter, and an air source of at least 60 pounds per squareinch, the following operational instructions have been found highlyeffective.

Setting of air control valves: Before loading abrasive into the tank,

(l) place lever 13 in closed" position.

(2) Pull handle 10 to out position, hold while turning on valve 44.v Theslightest build up of pressure will hold the filling valve I1 in closedposition, at which time the hand may be released from handle 1D.

(3) Adjust valve 46 to 6() lbs. per square inch.

(4) Hold the nozzle end of the hose |62 while adjusting valve 42 to 35lbs. per square inch.

(5) Close valve 44.

(6) Open valve 2| which will exhaust the air from the tank, and permitopening of valve I1. After the pressure in the tank has come down toatmospheric, valve 2| is closed.

This completes preliminary setting of control valves, before abrasive isplaced in the tank.

To fill the machine with abrasive:

(7) Check the interior of the tank for any foreign material by removingthe bail and cap of handhole 88 and inserting a hand and arm into thetank and probing to determine if there is any refuse at the bottom ofthe cone. A flash light may also be used to see the interior. Replaceall parts carefully.

(8) Handle 10 is pushed in so that the filling valve drops to its lowestposition.

(9) Pour about 5 cu. ft. of abrasive into the top of the tank. Theabrasive should not contain any coarse particles such as paper, matchstems, lint from cloth bags, etc.

(l0) The blast hose |02 should be held by the operator for blasting,before the next operation.

(l1) Pull handle 16 to close the filling valve, hold until valve 44 isturned on.

(12) Turn valve 44 on which admits air to the tank and hose line.(Valves were set at preliminary setting.)

(13) When tankA pressure is up to 60 lbs. per square inch, the controllever 13 may be pulled down to open position.

Abrasive should now be flowing from the nozzle.

The gauges will show a differential pressure of approximately 5 lbs. persquare inch, while blasting. The gauge on the tank pressure will be45-50 lbs., and the gauge on the blast line pressure will beapproximately 40-45 lbs. For soft abrasives it is necessary that thetank pressure be higher than the blast line pressure.

For pressures other than 60 lbs. per square inch, the dierentialpressure will be in approximately the same proportion.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope hereof, it is to beunderstood that this invention is not limited to the specificembodiments hereof, except as defined in the appended claims. Thus, theconduit I6 can be positioned in the hopper I2, and as far down as thelowest portion of the tank.

The height of the conduit is only limited by the ability of theavailable fluid pressure to effect agitation of the soft grits adjacentthe tank bottom, and about two feet is the practical maximum. Thedirecting holes I8 of the conduit need not be pointed straight down, butcan be tilted about 80 degrees up in any direction, although theagitation produced with such a construction is not quite as eilicient.

What is claimed is:

1. A pressure blast machine for projecting a stream of soft abrasiveparticles, said machine comprising a tank for receiving and storing aquantity of said particles, the bottom portion of said tank forming ahopper in free communication with the upper portion of the tank fordischarging said particles, a mixing chamber secured to said hopper forreceiving said discharged particles, said mixing chamber having anopening therein for receiving a stream of luid, under pressure, forimparting a projecting force upon said discharged particles, and ablasting opening for receiving and directing said particles and saidstream of fluid, tank pressurizing structure connected for introducingfluid under pressure into said tank, said structure including agitatingmeans within said tank for discharging at least one stream of lluid,under pressure, into said hopper to agitate said particles, and iluidpressure regulating elements connected to said mixing chamber andcontrolling the iluid operating pressure under which the projectingfluid is received, and maintaining this pressure below that at whichfluid is introduced into said tank to assure that the particles areuniformly discharged and do not jam in the bottom of the hopper, saidtank including a first conduit for carrying fluid to said agitatingmeans, a second conduit for carrying fluid to said mixing chamber, athird conduit common to both said rst and said second conduit forcarrying fluid to each from a common supply of fluid under pressure, thefluid pressure regulating elements are connected at least in said secondconduit, and the second conduit also has a check valve to resist themovement of particles from the mixing chamber to the pressure regulatingelements under the influence of the high tank pressure.

2. In a method of blasting articles with finely divided soft abrasiveparticles, the steps of maintaining the particles in a container,injecting into the container a fluid under pressure to agitate theparticles, supplying a stream of blastant fluid under a lowersuper-atmospheric pressure, mixing the agitated particles in the tankwith the blastant stream at their respective pressures to cause theparticles to be carried along with the stream, and directing said streamat the articles to be blasted.

3. A pressure blast machine for projecting a stream of soft abrasiveparticles, said machine comprising a tank for receiving and storing aquantity of said particles, the bottom portion of said tank `forming ahopper infree communication with the upper portion of the tank andterminating in an outlet through which it moves said particles, a mixingchamber secured to said outlet for receiving said moved particles, saidmixing chamber having a supply line opening therein for receiving streamof fluid, under pressure, to impart a projecting force upon theparticles received by the chamber, and a discharge opening for directingsaid particles and said stream of fluid, tank pressurizing structureconnected for introducing uid under pressure into said tank, saidstructure including agitating means within said tank for discharging atleast one stream of fluid under pressure into said hopper to agitate theparticles therein, and a pressure regulating valve connected in saidline to hold substantially fixed the projection-imparting pressure andmaintain it below the pressure at which fluid is introduced into thetank, to assure that the particles are uniformly discharged and do notjam in the bottom of the hopper.

FRANK NEWELL.

References Cited in the flle of this patent UNITED STATES PATENTS NumberName Date 979,897 Steedman Dec. 27, 1910 1,297,223 Mott Mar. 11, 1919'1,433,302 Rothchild Oct. 24, 1922 1,730,195 Davis Oct. 1, 19292,146,917 Rosenberger Feb. 14, 1939 2,324,425 Rasmussen July 13, 1943FOREIGN PATENTS Number Country Date 359,343 France Jan. 18, 19,06

